Immunomodulatory effects of a polysaccharide purified from Lepidium meyenii Walp. on macrophages

Introduction

Immunomodulatory agents are substances that can stimulate immune responses or maintain immune balance. Many reports have demonstrated that plant polysaccharides are ideal immunomodulators owing to their non-cytotoxic properties such as Cordyceps taii polysaccharide and Hericium erinaceus polysaccharide. Macrophages play a crucial role in the immune system. They are the first cells to recognize infectious agents, and they are central to cell-mediated and humoral immunity. After activation, macrophages synthesize and secrete nitric oxide, reactive oxygen species and cytokines, which function as mediators of the immune system. Immunomodulatory polysaccharides exhibit a variety of beneficial pharmacological effects via their ability to modulate macrophage immune function. An increasing number of researchers have focused on the study and exploitation of botanical polysaccharides with macrophage immunomodulatory activity.

Lepidium meyenii Walp., known as ‘maca’, belongs to the family Brassicae and is cultivated mainly in the central Andes of Peru. It has been used as food and traditional medicine in the region for over 2000 years. Recently, maca has received increasing research interest due to its pronounced widespread biological activities, such as improving sexual performance, antioxidant activit, preventing prostate hyperplasia, alleviating menopausal syndrome, antifatigue and immunomodulatory effects. However, recent studies of maca are mainly focused on the crude extract and some small molecular compounds, including glucosinolates, alkaloids and sterols. Investigations of high molecular weight constituents, i.e., polysaccharides, have only focused on the extraction and antioxidant activity of crude polysaccharide. Little attention has been devoted to the characterization and immunomodulatory activity of purified polysaccharides from maca. In this study, a polysaccharide of maca was isolated and purified. Its physicochemical properties and immunomodulatory effects on RAW264.7 were studied. Results of this study could instigate further research, and will ultimately help in developing novel functional foodstuff and drugs.